Polyimide powder for antistatic polyimide molded product and polyimide molded product thereby

ABSTRACT

A polyimide powder for an antistatic polyimide molded product is disclosed. The polyimide powder comprises a polyimide-powder prepared from an aromatic tetracarboxylic acid component and a diamine component, and a conductive carbon black having a DBP oil absorption of 300 ml/100 g or more; wherein the amount of the conductive carbon black is within a range of 0.75 wt % to 5 wt % relative to the polyimide-powder. A polyimide molded product with sufficient antistatic property can be formed by molding the above polyimide powder.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polyimide powder, which are preparedfrom an aromatic tetracarboxylic acid component and a diamine component,for forming a polyimide molded product with excellent heat resistanceand antistatic property. Furthermore, the present invention relates to amethod for forming an antistatic polyimide molded products from thepolyimide powder, and a polyimide molded product thereby.

2. Background Art

Previously, JP-A 1986-241,326 and JP-A 1989-266,134, for example,described methods for forming a molded product of polyimide-powdersprepared from an aromatic tetracarboxylic acid component, such as a3,3′,4,4′-biphenyltetracarboxylic acid component, and a diaminecomponent, such as a p-phenylenediamine component. These references showthat the above-mentioned molded products have excellent heat resistance,dimensional stability and mechanical strength such as compressivestrength.

However, it is known that the molded products of polyimide-powdersdescribed in the above-indicated references do not have slidability,abrasion resistance or antistatic property in itself. Accordingly, it isknown to improve these properties of a polyimide molded product byadding inorganic fine powders, other resins, graphite, or inorganicfibrous materials to polyimide-powders (JP-A 1987-132,960, JP-A1987-185,748 and JP-A 1988-81,160).

On the other hand, JP-B 1993-28,727 discloses an antistatic aromaticpolyimide film having improved antistatic property through the additionof sulfonates to polyimide. JP-A 2004-58,562 discloses an antistaticfilm produced by coating the surface of the polyimide film with themixture of a metal oxide and a conductive ultrafine particle.

SUMMARY OF THE INVENTION

According to the methods described in the above-mentioned references,however, the addition of carbon or graphite of 5.5 wt % to 100 wt %relative to the polyimide is needed for the improvement in the abrasionresistance or slidability of a polyimide molded product, andconsequently, the intrinsic properties of the polyimide may be impaired.

An object of the present invention is to provide a polyimide powder fromwhich a polyimide molded product with antistatic property can beprepared without significant degradation in the intrinsic properties ofthe polyimide. Another object of the present invention is to provide amethod for forming a polyimide molded product, and a polyimide moldedproduct with excellent properties by using such a polyimide powder.

The present invention relates to a polyimide powder for an antistaticpolyimide molded product, comprising

a polyimide-powder prepared from an aromatic tetracarboxylic acidcomponent and a diamine component, and

a conductive carbon black having a DBP oil absorption of 300 ml/100 g ormore;

wherein the amount of the conductive carbon black is within a range of0.75 wt % to 5 wt % relative to the polyimide-powder.

The present invention further relates to a method for forming anantistatic polyimide molded product, comprising the steps of:

filling a mold with the above-mentioned polyimide powder, and

applying a pressure and a heat to the polyimide powder for molding atthe same time or different times.

The present invention still further relates to an antistatic polyimidemolded product formed by the above-mentioned method.

According to the present invention, the conductive carbon black having aDBP oil absorption of 300 ml/100 g or more is added to thepolyimide-powder, to obtain a polyimide powder for an antistaticpolyimide molded product. The use amount of the carbon black is smallerand is 5 wt % or less relative to the polyimide-powder. By using thispolyimide powder, however, a polyimide molded product with sufficientantistatic property can be formed.

According to the present invention, there can be provided a polyimidemolded product with sufficient antistatic property as well as theintrinsic properties of the polyimide, and a method for forming thesame.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the present invention will be describedbelow.

1) The above-mentioned polyimide powder for an antistatic polyimidemolded product, wherein the amount of the conductive carbon black havinga DBP oil absorption of 300 ml/100 g or more is within a range of 1 wt %to 3 wt % relative to the polyimide-powder.

2) The above-mentioned polyimide powder for an antistatic polyimidemolded product, wherein the aromatic tetracarboxylic acid component ofthe polyimide-powder comprise 3,3′,4,4′-biphenyltetracarboxylicdianhydride.

3) The above-mentioned polyimide powder for an antistatic polyimidemolded product, wherein the polyimide-powder is made of

the aromatic tetracarboxylic acid component comprising3,3′,4,4′-biphenyltetracarboxylic dianhydride and2,3,3′,4′-biphenyltetracarboxylic dianhydride, and

the aromatic diamine component comprising at least 80 mol % ofp-phenylenediamine;

wherein a ratio of 2,3,3′,4′-biphenyltetracarboxylic dianhydride in awhole of the aromatic tetracarboxylic acid component is 0.5 mol % ormore and less than 30 mol %.

4) The above-mentioned polyimide powder for an antistatic polyimidemolded product, wherein the diamine component of the polyimide-powdercomprise p-phenylenediamine or 4,4′-diaminodiphenylether.

5) The above-mentioned method for forming an antistatic polyimide moldedproduct, wherein the molding of the polyimide powder is performed by ahot compression molding at a molding temperature of 350° C. to 600° C.and a molding pressure of 30 MPa to 2,000 MPa; or

a pre-molding at a molding temperature of room temperature to 350° C.and a molding pressure of 30 MPa to 2,000 MPa, and a post-sintering ofthe obtained pre-molded product without a compression at a temperatureof 350° C. to 600° C.

6) The above-mentioned antistatic polyimide molded product, wherein asurface resistivity of the antistatic polyimide molded product is withina range of 10⁴ Ω/□ to 10⁷ Ω/□.

In the present invention, the polyimide-powder may be prepared from apolyamic acid solution obtained by reacting an aromatic tetracarboxylicacid component with a diamine component in an organic polar solvent. Theexamples of an aromatic tetracarboxylic acid component include aromatictetracarboxylic dianhydrides, preferably3,3′,4,4′-biphenyltetracarboxylic dianhydride or pyromelliticdianhydride. The examples of a diamine component include aromaticdiamines, preferably p-phenylenediamine or 4,4′-diaminodiphenylether. Inthis scheme, the polyimide-powder may be prepared by isolating thepolyimide-precursor powder from the polyamic acid solution, and thenheating and drying the polyimide-precursor powder; or by heating thepolyamic acid solution for imidation, and then isolating and drying theresultant polyimide-powder.

A preferable polyimide-powder used in the present invention may beprepared from an aromatic tetracarboxylic acid component comprising anaromatic tetracarboxylic acid component which gives a crystallinearomatic polyimide and a tetracarboxylic acid component which gives anamorphous polyimide, in which the content of the tetracarboxylic acidcomponent which gives an amorphous polyimide is about 0.5 mol % or moreand less than 30 mol % relative to the whole of the tetracarboxylic acidcomponent, and an aromatic diamine component comprisingp-phenylenediamine at least about 80 mol % relative to the whole of thediamine component.

The preferable examples of an aromatic tetracarboxylic acid componentwhich gives a crystalline aromatic polyimide include3,3′,4,4′-biphenyltetracarboxylic acid, or dianhydride thereof, or anester thereof with a lower alcohol. The preferable examples of atetracarboxylic acid component which gives an amorphous polyimideinclude 2,3,3′,4′-biphenyltetracarboxylic acid, or dianhydride thereof,or an ester thereof with a lower alcohol. For both components,dianhydride is more preferable.

The ratio of the tetracarboxylic acid component which gives an amorphouspolyimide (preferably 2,3,3′,4′-biphenyltetracarboxylic acid component)in the whole of the tetracarboxylic acid component is preferably 1 mol %or more and less than 25 mol %, further preferably 1.5 mol % or more andless than 20 mol %.

As the above-mentioned aromatic tetracarboxylic acid component, only3,3′,4,4′-biphenyltetracarboxylic acid component (preferably3,3′,4,4′-biphenyltetracarboxylic dianhydride) and2,3,3′,4′-biphenyltetracarboxylic acid component (preferably2,3,3′,4′-biphenyltetracarboxylic dianhydride) by the above ratio ispreferably used, in view of a high level of properties (especiallymechanical strength and heat resistance when used) of the formed moldedproduct thereby. A portion, preferably 50 mol % or less, especially 20mol % or less, of the above biphenyltetracarboxylic acid components maybe replaced with other aromatic tetracarboxylic acid components.Examples of such aromatic tetracarboxylic acid component includepyromellitic acid or dianhydride thereof,3,3′,4,4′-benzophenonetetracarboxylic acid or dianhydride thereof,2,2′-bis(3,4-dicarboxyphenyl)propane or dianhydride thereof,bis(3,4-dicarboxyphenyl)methane or dianhydride thereof, andbis(3,4-dicarboxyphenyl)ether or dianhydride thereof.

In another preferred embodiment of the present invention,3,3′,4,4′-biphenyltetracarboxylic acid component (preferably3,3′,4,4′-biphenyltetracarboxylic dianhydride) is used alone as anaromatic tetracarboxylic acid component. 3,3′,4,4′-biphenyltetracarboxylic acid component may be used in combinationwith other aromatic tetracarboxylic acid components. In this case, theuse amount of other aromatic tetracarboxylic acid components ispreferably 50 mol % or less, especially 20 mol % or less relative to thewhole of the aromatic tetracarboxylic acid components.

As the above-mentioned aromatic diamine component, p-phenylenediamine ispreferably used alone, in view of the properties of the formed moldedproduct and ease of the polymerization/imidation operation. A smallportion, preferably about 20 mol % or less, of it may be replaced withother aromatic diamines as long as the properties of the product wouldnot be essentially impaired. Examples of such aromatic diamines includemetaphenylenediamine, 4,4′-diaminodiphenylether,4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane,bis(4-aminophenyl)dimethylsilane, 1,4-bis(4-amino-phenoxy)benzene and1,3-bis(4-amino-phenoxy)benzene.

In another preferred embodiment of the present invention, as a diaminecomponent, 4,4′-diaminodiphenylether is used alone.4,4′-diaminodiphenylether may be used in combination with other aromaticdiamines.

The preferable polyimide-powder can be obtained by polymerization andimidation of the above aromatic tetracarboxylic acid component and theabove aromatic diamine component with almost equimolar amount in anorganic polar solvent according to a known method, followed bycollection of the powder from the reaction system.

Preferably, the above-mentioned components may be polymerized in anorganic polar solvent at a temperature of 10° C. to 80° C. for 1 to 30hours, to give a polyamic acid (imidation ratio: 5% or less) solutionhaving a logarithmic viscosity of polymer (measurement temperature: 30°C.; concentration: 0.5 g/100 ml-solvent; solvent:N-methyl-2-pyrrolidone) of 5 or less, a polymer concentration of 25 wt %or less, and a rotational viscosity (30° C.) of 4,500 poises or less. Asthe organic polar solvent, there can be used those generally used forthe preparation of polyamic acids (polyimide precursors) such asN,N-dimethylacetamide or N-methyl-2-pyrrolidone. Subsequently, theobtained polyamic acid solution may be heated at a temperature of 160°C. to 300° C. for about 0.2 to 20 hours, whereby the imidation iscompleted.

In the present invention, the polyimide-powder preferably has a meanparticle size of 0.5 μm to 100 μm (a primary particle).

According to the present invention, a polyimide powder for an antistaticpolyimide molded product may be prepared by adding a conductive carbonblack having a DBP oil absorption of 300 ml/100 g or more by a ratio of0.75 wt % to 5 wt %, preferably 1 wt % to 3 wt % to the above-mentionedpolyimide-powder; and mixing them preferably homogeneously.

In the present invention, a conductive carbon black having a DBP oilabsorption of 300 ml/100 g or more is used as a conductive carbon blackadded to the polyimide-powder. If a conductive carbon black having a DBPoil absorption of less than 300 ml/100 g was used, the addition of alarge amount of carbon black to the polyimide-powder would be needed forachieving a surface resistivity of the polyimide molded product within arange of 10⁴ Ω/□ to 10⁷ Ω/□, with the result that the properties of thepolyimide molded product may be degraded or it may become difficult tomix the polyimide-powder and the carbon black homogeneously.

The examples of the conductive carbon black having a DBP oil absorptionof 300 ml/100 g or more include various ketjenblacks commerciallyavailable from Lion Corporation, such as Ketjenblack EC-600JD (powdery,DBP oil absorption: 495 ml/100 g) and Ketjenblack EC (powdery, DBP oilabsorption: 360 ml/100 g).

The DBP oil absorption of the conductive carbon black is preferablywithin a range of 300 ml/100 g to 550 ml/100 g in view of theiravailability and effectiveness.

The polyimide powder for an antistatic polyimide molded product of thepresent invention may be obtained by adding a given amount of aconductive carbon black to a polyimide-powder, and mixing them for about1 to 50 hours through a known method, preferably using a ball mill.

According to the present invention, a polyimide powder molded productmay be formed by filling a mold with the above-mentioned polyimidepowder for an antistatic polyimide molded product, and applying apressure and a heat to it for molding at the same time or differenttimes. Preferably, an antistatic polyimide molded product may be formedby a hot compression molding at a molding temperature of 350° C. to 600°C. and a molding pressure of 30 MPa to 2,000 MPa. It is also preferableto form an antistatic polyimide molded product by a pre-molding at amolding temperature of room temperature to 350° C. and a moldingpressure of 30 MPa to 2,000 MPa, and a post-sintering of the resultingpre-molded product without a compression at a temperature of 350° C. to600° C.

As an apparatus for forming the polyimide powder molded product, forexample, a four-column hydraulic press or a high-pressure hot press maybe employed. As for the pre-molded product, it may be preferably formed,for example, by using a rotary press or a tableting machine.

In the present invention, a surface resistivity of the polyimide moldedproduct may be determined according to JIS K6911. And, a DBP oilabsorption of a conductive carbon black may be determined according toASTM D2414.

EXAMPLES

The present invention is described below in more detail with referenceto Examples and Comparative Examples. However, the present invention isin no way restricted to the following Examples.

In the following description, the meanings of the abbreviations are asfollows.

NMP: N-methyl-2-pyrrolidone

PPD: p-phenylenediamine

a-BPDA: 2,3,3′,4′-biphenyltetracarboxylic dianhydride

s-BPDA: 3,3′,4,4′-biphenyltetracarboxylic dianhydride

ODA: 4,4′-diaminodiphenylether

Example 1

2987.89 g of NMP and 140.58 g (1.300 mol) of PPD as a diamine componentwere fed at 60° C. into a five-liter four-necked separable flaskequipped with a stirring machine, a reflux condenser (with a waterseparator), a thermometer and a nitrogen gas feed pipe. To the resultingliquid mixture were added 26.77 g (0.091 mol) of a-BPDA and 355.71 g(1.209 mol) of s-BPDA as a tetracarboxylic acid component almostsimultaneously, while stirring under a nitrogen stream. And then, theresulting liquid was stirred for 2 hours to give a solution uniformlydissolving each monomer component with NMP. Subsequently, the solutionwas heated up to 190° C. in about 60 minutes while stirring under anitrogen stream, refluxing the solvent and generated water, and removingthe generated water. The precipitation of polyimide-powder began toappear once the internal temperature reached around 165° C. After theinternal temperature reached 190° C., the temperature was kept constantfor three hours to complete the reaction. After that, the reactionliquid was cooled down, and the resulting polyimide-powder wasfiltrated, washed with acetone, dried in a vacuum at 150° C. for 10hours, and subsequently dried under atmospheric pressure at 300° C. for30 minutes to give the polyimide-powder.

To 400 g of the obtained polyimide-powder was added 8 g of theketjenblack (EC-600JD, Lion Corporation, DBP oil absorption: 495 ml/100g), followed by mixing with a ball mill for 24 hours to give thepolyimide powder for an antistatic polyimide molded product.

Example 2

A circular mold was filled with the polyimide powder for an antistaticpolyimide molded product obtained in Example 1, and was pre-heated at300° C. for 6 hours with a pressing lid off. Immediately after thepre-heating, the pressing lid was putted on the mold, and the mold wasplaced in a pressing machine heated at 300° C. previously, and washeated up to 450° C. in 6 hours while pressed at 200 MPa. As soon as thetemperature reached 450° C., the mold was cooled down to roomtemperature in 12 hours. And then, the antistatic polyimide moldedproduct of 100 mm in diameter and 25 mm in thickness was removed fromthe mold.

The entire surface of the resulting antistatic polyimide molded productwas black and has no colored spot, meaning excellent dispersibility.And, the surface resistivity was 5×10⁴ Ω/□.

Example 3

The powder for an antistatic polyimide molded product was prepared inthe same manner as in Example 1 except that the use amount of theketjenblack (EC-600JD, Lion Corporation, DBP oil absorption: 495 ml/100g) was 4 g.

Then, in the same manner as in Example 2 except for using this powderfor an antistatic polyimide molded product, was formed the antistaticpolyimide molded product.

The entire surface of the resulting antistatic polyimide molded productwas black and has no colored spot, meaning excellent dispersibility.And, the surface resistivity was 3×10⁴ Ω/□.

Example 4

The powder for an antistatic polyimide molded product was prepared inthe same manner as in Example 1 except for using 382.49 g (1.300 mol) ofs-BPDA only as a tetracarboxylic acid component.

Then, in the same manner as in Example 2 except for using this powderfor an antistatic polyimide molded product, was formed the antistaticpolyimide molded product.

The entire surface of the resulting antistatic polyimide molded productwas black and has no colored spot, meaning excellent dispersibility.And, the surface resistivity was 5×10⁴ Ω/□.

Example 5

The powder for an antistatic polyimide molded product was prepared inthe same manner as in Example 1 except for using 382.49 g (1.300 mol) ofs-BPDA as a tetracarboxylic acid component and 260.31 g (1.300 mol) ofODA as a diamine component.

Then, in the same manner as in Example 2 except for using this powderfor an antistatic polyimide molded product, was formed the antistaticpolyimide molded product.

The entire surface of the resulting antistatic polyimide molded productwas black and has no colored spot, meaning excellent dispersibility.And, the surface resistivity was 5×10⁴ Ω/□.

Comparative Example 1

The powder for an antistatic polyimide molded product was prepared inthe same manner as in Example 1 except for using the conductive carbonblack (3350B, Mitsubishi Chemical Corporation, DBP oil absorption: 165ml/100 g) as a carbon black.

Then, in the same manner as in Example 2 except for using this powderfor an antistatic polyimide molded product, was formed the polyimidemolded product.

Several parts of the surface of the resulting polyimide molded producthave colored spots, meaning low dispersibility. And, the surfaceresistivity was 4×10¹⁵ Ω/□.

Comparative Example 2

The powder for an antistatic polyimide molded product was prepared inthe same manner as in Example 1 except for using 40 g of the graphite(ACP, Nippon Graphite Industries, Ltd., DBP oil absorption: 100 ml/100g) as a carbon black.

Then, in the same manner as in Example 2 except for using this powderfor an antistatic polyimide molded product, was formed the polyimidemolded product.

Several parts of the surface of the resulting polyimide molded producthave colored spots, meaning slightly low dispersibility. And, thesurface resistivity was 4×10⁸ Ω/□.

The particle sizes of the powders obtained in Examples 1 to 5 for anantistatic polyimide molded product were determined to be 20 μm or lessthrough a measurement with SEM photographs (5000-fold magnification).

1. A polyimide powder for an antistatic polyimide molded product,comprising a polyimide-powder prepared from an aromatic tetracarboxylicacid component and a diamine component, and a conductive carbon blackhaving a DBP oil absorption of 300 ml/100 g or more; wherein the amountof the conductive carbon black is within a range of 0.75 wt % to 5 wt %relative to the polyimide-powder.
 2. A polyimide powder for anantistatic polyimide molded product according to claim 1, wherein theamount of the conductive carbon black is within a range of 1 wt % to 3wt % relative to the polyimide-powder.
 3. A polyimide powder for anantistatic polyimide molded product according to claim 1, wherein thearomatic tetracarboxylic acid component of the polyimide-powdercomprises 3,3′,4,4′-biphenyltetracarboxylic dianhydride.
 4. A polyimidepowder for an antistatic polyimide molded product according to claim 1,wherein the polyimide-powder is made of the aromatic tetracarboxylicacid component comprising 3,3′,4,4′-biphenyltetracarboxylic dianhydrideand 2,3,3′,4′-biphenyltetracarboxylic dianhydride, and the aromaticdiamine component comprising at least 80 mol % of p-phenylenediamine;wherein a ratio of 2,3,3′,4′-biphenyltetracarboxylic dianhydride in awhole of the aromatic tetracarboxylic acid component is 0.5 mol % ormore and less than 30 mol %.
 5. A polyimide powder for an antistaticpolyimide molded product according to claim 1, wherein the diaminecomponent of the polyimide-powder comprises p-phenylenediamine or4,4′-diaminodiphenylether.
 6. A method for forming an antistaticpolyimide molded product, comprising the steps of: filling a mold with apolyimide powder according to claim 1, and applying a pressure and aheat to the polyimide powder for molding at the same time or differenttimes.
 7. A method for forming an antistatic polyimide molded productaccording to claim 6, wherein the molding of the polyimide powder isperformed by a hot compression molding at a molding temperature of 350°C. to 600° C. and a molding pressure of 30 MPa to 2,000 MPa; or apre-molding at a molding temperature of room temperature to 350° C. anda molding pressure of 30 MPa to 2,000 MPa, and a post-sintering of theobtained pre-molded product without a compression at a temperature of350° C. to 600° C.
 8. An antistatic polyimide molded product formed by amethod according to claim
 6. 9. An antistatic polyimide molded productaccording to claim 8, wherein a surface resistivity of the antistaticpolyimide molded product is within a range of 10⁴ Ω/□ to 10⁷ Ω/□.
 10. Apolyimide powder product comprising: a polyimide powder which is apolymerized and imidated product of an aromatic tetracarboxylic acidcomponent and a diamine component; and a conductive carbon black havinga DBP oil absorption of 300 ml/100 g or more, said conductive carbonblack being homogeneously mixed with the polyimide powder in an amountof 0.75 wt % to 5 wt % relative to the polyimide powder.
 11. Thepolyimide powder product according to claim 10, wherein the polyimidepowder has a mean particle size of 0.5 μm to 100 μm as a primaryparticle.
 12. The polyimide powder product according to claim 10,wherein the amount of the conductive carbon black is within a range of 1wt % to 3 wt % relative to the polyimide-powder.
 13. The polyimidepowder product according to claim 10, wherein the aromatictetracarboxylic acid component comprises3,3′,4,4′-biphenyltetracarboxylic dianhydride.
 14. The polyimide powderproduct according to claim 13, wherein the aromatic tetracarboxylic acidcomponent further comprises 2,3,3′,4′-biphenyltetracarboxylicdianhydride in an amount of 0.5 mol % or more but less than 30 mol % ofthe aromatic tetracarboxylic acid component.
 15. The polyimide powderproduct according to claim 10, wherein the aromatic diamine componentcomprises p-phenylenediamine or 4,4′-diaminodiphenylether.
 16. Thepolyimide powder product according to claim 15, wherein the aromaticdiamine component comprises at least 80 mol % of p-phenylenediamine. 17.A method for forming an antistatic polyimide molded product, comprisingthe steps of: providing a polyimide powder product of claim 10; fillinga mold with the polyimide powder product; and applying pressure and heatto the polyimide powder product in the mold, thereby obtaining anantistatic polyimide molded product.
 18. The method according to claim17, wherein the antistatic polyimide molded product has a surfaceresistivity within a range of 10⁴ Ω/□ to 10⁷ Ω/□.